The System Partition is the partition that contains the startup files, like NTDetect.com, NTLDR, and Boot.ini. The Boot Partition contains the system files (%SystemRoot%\System32).
If you compress the boot partition on a computer that is running Windows Server 2003, Windows XP, or Windows 2000, and subsequently update a driver by installing a file that does not have a digital signature, the installation appears to be successful, but the driver is not updated.
NOTE: If you compress the boot partition, any previously installed drivers without a digital signature will revert to a previous version.
This behavior is the result of WFP (Windows File Protection). When you write a compressed file into a protected folder, WFP replaces it from the DLLCache.
To workaround this behavior, if you compress the boot partition, DO NOT compress the root directory and DO NOT compress the Windows directory (%SystemRoot%).
NOTE: You can also ask the company that released the driver for a digitally signed copy.
NOTE: In Windows 2000, the %SystemRoot% folder is \WinNT. In all later versions of Windows, the %SystemRoot% folder is \Windows.